feat: add upload policies, daily limits, and storage quotas

- Add environment variables to configure anonymous uploads, daily upload caps, and default user storage limits.
- Update config loader to parse and validate the new settings.
- Implement backend logic to track daily usage and active storage per user.
- Update README and `.env.example` to document the new settings and admin panels.

backend/libs/handlers/manage.go

@@ -26,7 +26,7 @@ func (a *App) ManageBox(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	a.renderer.Render(w, http.StatusOK, "manage.html", web.PageData{
+	a.renderPage(w, r, http.StatusOK, "manage.html", web.PageData{
 		Title:       "Manage upload",
 		Description: "Delete this anonymous Warpbox upload.",
 		Data:        a.managePageData(box, r.PathValue("token")),
@@ -48,7 +48,7 @@ func (a *App) ManageDeleteBox(w http.ResponseWriter, r *http.Request) {
 }
 
 func (a *App) ManageDeleted(w http.ResponseWriter, r *http.Request) {
-	a.renderer.Render(w, http.StatusOK, "manage_deleted.html", web.PageData{
+	a.renderPage(w, r, http.StatusOK, "manage_deleted.html", web.PageData{
 		Title:       "Upload deleted",
 		Description: "This Warpbox upload has been deleted.",
 		Data:        boxView{ID: r.PathValue("boxID")},